Drop commented code_is_good lines

Marlin/Marlin_main.cpp

       case 92: // G92
         gcode_G92();
         break;
-
-      // default: code_is_good = false;
     }
     break;
 
       case 999: // M999: Restart after being Stopped
         gcode_M999();
         break;
-
-      // default: code_is_good = false;
     }
     break;